An electric vehicle or a hybrid electric vehicle requires a power source having a large capacity and hence, an energy storage apparatus which includes a plurality of energy storage devices is used. An energy storage apparatus of this type includes: an energy storage device group which includes a plurality of energy storage devices arranged in a row in a first direction; and a holder which holds the energy storage device group (see JP-A-9-76769, for example). The holder includes: a pair of terminal members which directly or indirectly sandwiches the energy storage device group in the first direction; and a frame which connects the pair of terminal members to each other.
In the above-mentioned energy storage apparatus, both ends of the energy storage device group in the first direction are supported by the pair of terminal members and hence, when the number of energy storage devices is increased, the whole length of the energy storage device group in the first direction is increased. Accordingly, in the above-mentioned energy storage apparatus, there may be a case where, due to the increase of the whole length of the energy storage device group in the first direction, a resonance frequency of the energy storage device group is lowered.